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Network Working Group J. Postel
Request for Comments: 858 J. Reynolds
ISI
Obsoletes: NIC 15392 May 1983
TELNET SUPPRESS GO AHEAD OPTION
This RFC specifies a standard for the ARPA Internet community. Hosts on
the ARPA Internet are expected to adopt and implement this standard.
1. Command Name and Code
SUPPRESS-GO-AHEAD 3
2. Command Meanings
IAC WILL SUPPRESS-GO-AHEAD
The sender of this command requests permission to begin
suppressing transmission of the TELNET GO AHEAD (GA) character
when transmitting data characters, or the sender of this command
confirms it will now begin suppressing transmission of GAs with
transmitted data characters.
IAC WON'T SUPPRESS-GO-AHEAD
The sender of this command demands to begin transmitting, or to
continue transmitting, the GA character when transmitting data
characters.
IAC DO SUPPRESS-GO-AHEAD
The sender of this commannd requests that the sender of data start
suppressing GA when transmitting data, or the sender of this
command confirms that the sender of data is expected to suppress
transmission of GAs.
IAC DON'T SUPPRESSS-GO-AHEAD
The sender of this command demands that the receiver of the
command start or continue transmitting GAs when transmitting data.
3. Default
WON'T SUPPRESS-GO-AHEAD
DON'T SUPPRESS-GO-AHEAD
Go aheads are transmitted.
RFC 858 May 1983
4. Motivation for the Option
While the NVT nominally follows a half duplex protocol complete with
a GO AHEAD signal, there is no reason why a full duplex connection
between a full duplex terminal and a host optimized to handle full
duplex terminals should be burdened with the GO AHEAD signal.
Therefore, it is desirable to have a TELNET option with which parties
involved can agree that one or the other or both should suppress
transmission of GO AHEADS.
5. Description of the Option
When the SUPPRESS-GO-AHEAD option is in effect on the connection
between a sender of data and the receiver of the data, the sender
need not transmit GAs.
It seems probable that the parties to the TELNET connection will
suppress GO AHEAD in both directions of the TELNET connection if GO
AHEAD is suppressed at all; but, nonetheless, it must be suppressed
in both directions independently.
With the SUPPRESS-GO-AHEAD option in effect, the IAC GA command
should be treated as a NOP if received, although IAC GA should not
normally be sent in this mode.
6. Implementation Considerations
As the SUPRESS-GO-AHEAD option is sort of the opposite of a line at a
time mode, the sender of data which is suppressing GO AHEADs should
attempt to actually transmit characters as soon as possible (i.e.,
with minimal buffering) consistent with any other agreements which
are in effect.
In many TELNET implementations it will be desirable to couple the
SUPPRESS-GO-AHEAD option to the echo option so that when the echo
option is in effect, the SUPPRESS-GO-AHEAD option is in effect
simultaneously: both of these options will normally have to be in
effect simultaneously to effect what is commonly understood to be
character at a time echoing by the remote computer.

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